| Message ID | 20230614131746.3670303-1-songshuaishuai@tinylab.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | memblock: Add error message when memblock_can_resize is not ready | expand |
Hi, On Wed, Jun 14, 2023 at 09:17:46PM +0800, Song Shuai wrote: > The memblock APIs are always correct, thus the callers usually don't > handle the return code. But the failure caused by unready memblock_can_resize > is hard to recognize without the return code. Like this piece of log: Please make it clear that failure is in memblock_double_array(), e.g. But when memblock_double_array() is called before memblock_can_resize is true, it is hard to understand the actual reason for the failure. > > ``` > [ 0.000000] memblock_phys_alloc_range: 4096 bytes align=0x1000 from=0x0000000000000000 max_addr=0x0000000000000000 alloc_pmd_fixmap+0x14/0x1c > [ 0.000000] memblock_reserve: [0x000000017ffff000-0x000000017fffffff] memblock_alloc_range_nid+0xb8/0x128 > [ 0.000000] Oops - store (or AMO) access fault [#1] > ``` > > So add an error message for this kind of failure: > > ``` > [ 0.000000] memblock_phys_alloc_range: 4096 bytes align=0x1000 from=0x0000000000000000 max_addr=0x0000000000000000 alloc_pmd_fixmap+0x14/0x1c > [ 0.000000] memblock_reserve: [0x000000017ffff000-0x000000017fffffff] memblock_alloc_range_nid+0xb8/0x128 > [ 0.000000] memblock: Can't double reserved array for area start 0x000000017ffff000 size 4096 > [ 0.000000] Oops - store (or AMO) access fault [#1] > ``` > > Signed-off-by: Song Shuai <songshuaishuai@tinylab.org> > --- > mm/memblock.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/memblock.c b/mm/memblock.c > index 3feafea06ab2..ab952a164f62 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -418,8 +418,11 @@ static int __init_memblock memblock_double_array(struct memblock_type *type, > /* We don't allow resizing until we know about the reserved regions > * of memory that aren't suitable for allocation > */ > - if (!memblock_can_resize) > + if (!memblock_can_resize) { > + pr_err("memblock: Can't double %s array for area start %pa size %ld\n", > + type->name, &new_area_start, (unsigned long)new_area_size); Most of the time memblock uses %llu and cast to u64 to print size, please make this consistent. > return -1; > + } > > /* Calculate new doubled size */ > old_size = type->max * sizeof(struct memblock_region); > -- > 2.20.1 > >
Sorry for not replying to you in time 在 2023/6/15 00:07, Mike Rapoport 写道: > Hi, > > On Wed, Jun 14, 2023 at 09:17:46PM +0800, Song Shuai wrote: >> The memblock APIs are always correct, thus the callers usually don't >> handle the return code. But the failure caused by unready memblock_can_resize >> is hard to recognize without the return code. Like this piece of log: > > Please make it clear that failure is in memblock_double_array(), e.g. > Having numerous memblock reservations at early boot where memblock_can_resize is unset may exhaust the INIT_MEMBLOCK_REGIONS sized memblock.reserved regions and try to double the region array via memblock_double_array() which fails and returns -1 to the caller. You can find the numerous memblock reservations reported by this commit 24cc61d8cb5a ("arm64: memblock: don't permit memblock resizing until linear mapping is up"). And the similar test sense can be simulated by a constructed dtb with numerous discrete /memreserve/ or /reserved-memory regions. > But when memblock_double_array() is called before memblock_can_resize > is true, it is hard to understand the actual reason for the failure. > >> >> ``` >> [ 0.000000] memblock_phys_alloc_range: 4096 bytes align=0x1000 from=0x0000000000000000 max_addr=0x0000000000000000 alloc_pmd_fixmap+0x14/0x1c >> [ 0.000000] memblock_reserve: [0x000000017ffff000-0x000000017fffffff] memblock_alloc_range_nid+0xb8/0x128 >> [ 0.000000] Oops - store (or AMO) access fault [#1] >> ``` >> >> So add an error message for this kind of failure: >> >> ``` >> [ 0.000000] memblock_phys_alloc_range: 4096 bytes align=0x1000 from=0x0000000000000000 max_addr=0x0000000000000000 alloc_pmd_fixmap+0x14/0x1c >> [ 0.000000] memblock_reserve: [0x000000017ffff000-0x000000017fffffff] memblock_alloc_range_nid+0xb8/0x128 >> [ 0.000000] memblock: Can't double reserved array for area start 0x000000017ffff000 size 4096 >> [ 0.000000] Oops - store (or AMO) access fault [#1] >> ``` >> >> Signed-off-by: Song Shuai <songshuaishuai@tinylab.org> >> --- >> mm/memblock.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/mm/memblock.c b/mm/memblock.c >> index 3feafea06ab2..ab952a164f62 100644 >> --- a/mm/memblock.c >> +++ b/mm/memblock.c >> @@ -418,8 +418,11 @@ static int __init_memblock memblock_double_array(struct memblock_type *type, >> /* We don't allow resizing until we know about the reserved regions >> * of memory that aren't suitable for allocation >> */ >> - if (!memblock_can_resize) >> + if (!memblock_can_resize) { >> + pr_err("memblock: Can't double %s array for area start %pa size %ld\n", >> + type->name, &new_area_start, (unsigned long)new_area_size); > > Most of the time memblock uses %llu and cast to u64 to print size, please > make this consistent. I will fix it in next version if the above description is ok for you. > >> return -1; >> + } >> >> /* Calculate new doubled size */ >> old_size = type->max * sizeof(struct memblock_region); >> -- >> 2.20.1 >> >> >
On Tue, Jun 20, 2023 at 03:04:55PM +0800, Song Shuai wrote: > Sorry for not replying to you in time > > 在 2023/6/15 00:07, Mike Rapoport 写道: > > Hi, > > > > On Wed, Jun 14, 2023 at 09:17:46PM +0800, Song Shuai wrote: > > > The memblock APIs are always correct, thus the callers usually don't > > > handle the return code. But the failure caused by unready memblock_can_resize > > > is hard to recognize without the return code. Like this piece of log: > > > > Please make it clear that failure is in memblock_double_array(), e.g. > > > > Having numerous memblock reservations at early boot where > memblock_can_resize is unset > may exhaust the INIT_MEMBLOCK_REGIONS sized memblock.reserved regions and > try to > double the region array via memblock_double_array() which fails and returns > -1 to the caller. > > You can find the numerous memblock reservations reported by this commit > 24cc61d8cb5a ("arm64: memblock: don't permit memblock resizing until linear > mapping is up"). > And the similar test sense can be simulated by a constructed dtb with > numerous discrete > /memreserve/ or /reserved-memory regions. Ideally, the callers of memblock_reserve() should check the return value and panic with a meaningful message if it fails. Still, for now something like this patch is an improvement. How about we make the changelog to be something like: Subject: memblock: report failures when memblock_can_resize is not set The callers of memblock_reserve() do not check the return value presuming that memblock_reserve() always succeeds, but there are cases where it may fail. Having numerous memblock reservations at early boot where memblock_can_resize is unset may exhaust the INIT_MEMBLOCK_REGIONS sized memblock.reserved regions array and an attempt to double this array via memblock_double_array() will fail and will return -1 to the caller. When this happens the system crashes anyway, but it's hard to identify the reason for the crash. Add a panic message to memblock_double_array() to aid debugging of the cases when too many regions are reserved before memblock can resize memblock.reserved array. > > But when memblock_double_array() is called before memblock_can_resize > > is true, it is hard to understand the actual reason for the failure. > > > > > > > > ``` > > > [ 0.000000] memblock_phys_alloc_range: 4096 bytes align=0x1000 from=0x0000000000000000 max_addr=0x0000000000000000 alloc_pmd_fixmap+0x14/0x1c > > > [ 0.000000] memblock_reserve: [0x000000017ffff000-0x000000017fffffff] memblock_alloc_range_nid+0xb8/0x128 > > > [ 0.000000] Oops - store (or AMO) access fault [#1] > > > ``` > > > > > > So add an error message for this kind of failure: > > > > > > ``` > > > [ 0.000000] memblock_phys_alloc_range: 4096 bytes align=0x1000 from=0x0000000000000000 max_addr=0x0000000000000000 alloc_pmd_fixmap+0x14/0x1c > > > [ 0.000000] memblock_reserve: [0x000000017ffff000-0x000000017fffffff] memblock_alloc_range_nid+0xb8/0x128 > > > [ 0.000000] memblock: Can't double reserved array for area start 0x000000017ffff000 size 4096 > > > [ 0.000000] Oops - store (or AMO) access fault [#1] > > > ``` > > > > > > Signed-off-by: Song Shuai <songshuaishuai@tinylab.org> > > > --- > > > mm/memblock.c | 5 ++++- > > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > > > diff --git a/mm/memblock.c b/mm/memblock.c > > > index 3feafea06ab2..ab952a164f62 100644 > > > --- a/mm/memblock.c > > > +++ b/mm/memblock.c > > > @@ -418,8 +418,11 @@ static int __init_memblock memblock_double_array(struct memblock_type *type, > > > /* We don't allow resizing until we know about the reserved regions > > > * of memory that aren't suitable for allocation > > > */ > > > - if (!memblock_can_resize) > > > + if (!memblock_can_resize) { > > > + pr_err("memblock: Can't double %s array for area start %pa size %ld\n", > > > + type->name, &new_area_start, (unsigned long)new_area_size); The system will crash anyway if we get, here, so why won't use panic? Also, dumping new_area_start here does not add any information but rather confuses. How about panic("memblock: cannot resize %s array\n", type->name); > > > > Most of the time memblock uses %llu and cast to u64 to print size, please > > make this consistent. > I will fix it in next version if the above description is ok for you. > > > > > return -1; > > > + } > > > /* Calculate new doubled size */ > > > old_size = type->max * sizeof(struct memblock_region); > > -- > Thanks > Song Shuai > >
diff --git a/mm/memblock.c b/mm/memblock.c index 3feafea06ab2..ab952a164f62 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -418,8 +418,11 @@ static int __init_memblock memblock_double_array(struct memblock_type *type, /* We don't allow resizing until we know about the reserved regions * of memory that aren't suitable for allocation */ - if (!memblock_can_resize) + if (!memblock_can_resize) { + pr_err("memblock: Can't double %s array for area start %pa size %ld\n", + type->name, &new_area_start, (unsigned long)new_area_size); return -1; + } /* Calculate new doubled size */ old_size = type->max * sizeof(struct memblock_region);
The memblock APIs are always correct, thus the callers usually don't handle the return code. But the failure caused by unready memblock_can_resize is hard to recognize without the return code. Like this piece of log: ``` [ 0.000000] memblock_phys_alloc_range: 4096 bytes align=0x1000 from=0x0000000000000000 max_addr=0x0000000000000000 alloc_pmd_fixmap+0x14/0x1c [ 0.000000] memblock_reserve: [0x000000017ffff000-0x000000017fffffff] memblock_alloc_range_nid+0xb8/0x128 [ 0.000000] Oops - store (or AMO) access fault [#1] ``` So add an error message for this kind of failure: ``` [ 0.000000] memblock_phys_alloc_range: 4096 bytes align=0x1000 from=0x0000000000000000 max_addr=0x0000000000000000 alloc_pmd_fixmap+0x14/0x1c [ 0.000000] memblock_reserve: [0x000000017ffff000-0x000000017fffffff] memblock_alloc_range_nid+0xb8/0x128 [ 0.000000] memblock: Can't double reserved array for area start 0x000000017ffff000 size 4096 [ 0.000000] Oops - store (or AMO) access fault [#1] ``` Signed-off-by: Song Shuai <songshuaishuai@tinylab.org> --- mm/memblock.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)